Tcpip

http://fasterdata.es.net/TCP-tuning/ Excellent site provides both theoretical background and practical recommendation for the situation when you need to push limits of TCP links using regular OS and commodity hardware. Especially useful if you need to do it via long-haul fast TCP link, i.e. the situation when you normally use specialized networking hardware (read: cisco)

http://www.ibm.com/developerworks/linux/library/l-linux-networking-stack/?ca=dgr-lnxw01lnxNetStack very basic description on linux kernel network stack, but contains a list of follow-up literature, so it’s a useful article, even if you are not a beginner